Stabilization of fuel oils



'United. States Patent Pa., assignors to Gulf Research & DevelopmentCompany, Pittsburgh, Pa., acorporation of Delaware No Drawing. Filed May31", 1957, Ser. No. 662,584

7 Claims. (Cl.-4462)' This invention relates to stabilization of blendeddistillate fuel oils. More particularly, the invention relates tostabilization of mixtures of catalytic'ally cracked and straight runfuel oil distillates during storage at ambient atmospheric temperatures.I

Uncompounded distillate fuel oil compositions are often troublesome withregard to sludge deposition and color degradation during storage atnormal atmospheric temperatures. Sludge deposits in distillate fuel oilsare objectionable in that such deposits can causeclogging of burnerfilters, screens, nozzles, etc., and thereby lead to improperfunctioning of the combustion apparatusi'n which the fuel oil isconsumed.

. Although sludge deposition sometimes occurs in straight run distillatefuel oils and frequently occurs to a substantial degree in catalyticallycracked fuel oil dis-v tillates, sludge deposition in blends of straightrun and c'atalytically cracked fuel oil distillates presents an entirelydistinct problem from that encountered with either component oil. Whilethe sludge formed in such blended oils probably contains some sludge ofthe type formed by each component oil, the sludge formed in blended fueloils is of different composition and is consistently greatly in excessof the amount that can be accounted for from the known sludgingtendencies of the individual component oils.

It has heretofore been proposed to inhibit sludge deposition from mixeddistillate fuel oils by incorporation therein of oil-soluble chemicalinhibitors which are consumed during combustion of the oil.

It has now been found that sludge deposition in such mixed oils can begreatly alleviated by maintaining. the

oil in contact with an oil-insoluble inhibitor during;-

storage, which inhibitor can be used repeatedly and which is notconsumed during combustion. The present invention, based on thisdiscovery, relates to a process for improving the stability of mixed,catalytically cracked and straight run distillate fuel oils, andparticularly to improving the stability of the mixed oils with respectto sludge deposition in order to improve the appearance of such oils andto render them more effective for use in fuel oil furnaces and the like,even after being stored for extended periods. We have found thatimproved storage stability in the mixed distillate fuel oils can beobtained by maintaining the mixed oils during storage at ambientatmospheric temperatures in contact with a sludge-inhibiting proportionof an oil-insoluble, strongly basic, anion exchange resin. Stronglybasic anion exchange resins comprise a polymeric matrix having a.plurality of quaternary ammonium hydroxide groups 'associated therewith.Typical of the class are resins comprising the hydroxide form of atertiary aminequaternized, haloalkylated copolymer of about 80 to 99.9percent of a monovinyl aromatic hydrocarbon and about 0.1 to percent ofa divinyl aromatic hydrocarbon. We"

have also found that the moisture content of the resin is importantinsofar as the stability of the fuel oil is concerned. For best resultsthe resin should" contain at least about percent water, and preferablyfrom about percent water up to the pointof saturation. Co' polymerscontaining 0.5 to 6 percent divinyl aromatic 2,980,517 Patented Apr. 18,1961 reduced fouling tendencies and greater exchange capaci ties in fueloils; By way of example, excellent results are obtainable with astrongly basic anion exchange resin that comprises the hydroxide form ofa dimethyl ethanol amine-quaternized, chloromethylated copolymer ofabout 99 percent styrene and about 1 percent divinyl benzene, thatcontains about 55' percent moisture. Copolymers of other monovinyl anddivinyl aromatic hydrocarbo'nscan be used: For example, monovinylaromatic hydrocarbons capable of forming copolymers within the scope ofthe invention are typified by the following: styrene, orthometaandpara-methyl styrenes, ortho'-, metaand para? ethyl styrenes, vinylnaphthalene, vinyl anthracen'e, and their homologues. Examples ofdivinyl aromatic hydrocarbons that can' form copolymers included withinthe scope of the invention include divinyl benzene, divinyl" toluenes,divinyl naphthalene, divinyl ethyl benzenes', divinyl xylenes, and theirhomologues. An example of a preferred'haloalkyl group is thechloromethyl group. Examples of other haloalkyl' groups includechlorobutyl, bromoethyl, and the like. Preferred tertiary aminequaternizing agents include dimethyl ethanol amine and trimethyl' amine.Other suitable quaternizing agents in: clude triethyl andtripropylamines, dimethyl ethyl amine} diethyl cyclohexyl amine,tricyclohexyl amine, triph'enyl amine, diphenyl ethyl amine, benzyldimethyl amine, benzyl phenylmethyl amine, methyl diethanolamine, methylethyl propanol amine, etc; Additional examples of resins included by theprocess of this invention include the hydroxide form of a diethylcyclohexyl amine quaternized chlorobutylated copolymer of 96 p'ercenmeta-methyl styrene and 4 percent divinyl benzene,an"d" the hydroxideform of a benzyl phenyl methyl mine quaterni-zed bromoethylatedcopolymer of 94 percent vinyl naphthalene and 6 percent divinyl xylene,each in a moisture saturated condition. 7 i

The predominant non-crosslinked portion of the chin:- I

ride form of a tertiary amine-quaternized haloalkylatedcopolymer ofvinyl and divinyl aromatic hydrocarbons, for example, a trimethylamine-quaternized chloromethylated copolymer of styrene and divinylbenzene can be represented by the following structural formula:

whereas the crosslinked portion can be representedas In'the hydroxideform, the chlorine atoms are substituted with hydroxyl' groups in theabove structures.

It has not been determined exactly in what way the strongly basic anionexchange resins function to improve the stability of the mixed fueloils. Accordingly, the invention is not limited to any particular theoryof op eration. exchange resins act toremove impurities of anon-hydrocarbon nature, such as mercaptans, naphthenic acids,

hydrocarbons are particularly valuable because of phenols, etc., fromthe oil. However, thispo s'sibility is mo're'or' less negatived by thefact that mere percolation It'might appear that the strongly basic anion:a'lyze formation of sludge and color bodies.

exchange resins definitely do not function as sludge dissurface area.

' mum proportion of the resin. tical standpoint, it will normallyheu-ndesirable to employ more than about percent resin by'weight' of thecording to the method of'this invention showed no ,sig-,

see er? vtaining the desired stability in the fuel oils, or at any timenificant changes, as compared with an untreated sample may be that theanionexchang'e resins act to remove sludge and color precursors astheyare formed. The sludge and color precursors mayin and of: themselvesform sludge and color bodies, or they may merely cat- The anionpe'rsants, as they are entirelyinsolublein fueloil.

' The resinzoil proportions that are effective for the purposes of thisinventionwill vary' primarily accordingto the degree ofcontactbetweenthe resin and the fuel oil.

'bef orethis pointlhas been reached, the resins can be regeneraetd bytreatment with aqueous caustic, that is, sodium hydroxide- The. methodof regenerating spent anion exchange resins with aqueous caustic isconventional andneed not be described. in detail here. I

The stability problem with which the present invention is concernedexists when, a catalytically cracked and a straight-run oil are combinedin such proportions as to cause a substantial, combined sludging effectof the Y type described above. Theinvention is important when the ratioof the volume of the catalytically cracked oil to thestraight run oiliswithin the range of 9:1 to 1:9.

I The invention is especially advantageous when; applied to mixed fueloils containing these oils in a volume ratio The commercial resins aspurchased, before conversion in the shape of small granules or' beads ofrelatively large For this reason, the degree of interfacial' contactbetween oil andresin is potentially. large, particularly in the easedthe porous resin particles. Under I r rich inultraviolet rays, forperiods of 4 hours alternated r ample, an improvement instabilitycan beobtained using as little as about 0.004 weight percent resin,particularly where the oil or the resin is circulated'to' improvetheinterfacial contact. Normally, about 0.05 to'5'weight perce ntresinwill eltect a substantial improvement in the,

stability of theoil. Since the anion exchange resins are oil-insoluble,there is no need, other than as maybe imposed by "practicalconsiderations, to' restrict the maxi- However, from a mad oil. t

The desired intercontact between oil' and resin can be obtained inanyconvenient way in the storage containers For example. one or a number ofoil-permeable containers containing small portions of the resin can besuspended at suitably spaced locations in the oil. Alternatively,permeable containers containing the resin can be suspended from aplurality of radially disposed arms which can be rotated continuously orintermittently to obtain the desired intercontact. Suitable permeablecontainers have been prepared from muslin, linen and nylon fabric (wovenand unwoven) and from stainless steelscreen. Another way of obtainingthe desired intercon tact is to circulate the oil from the main storage,vessel through a bypass containing the resin. Still another method isto provide a lining for the storage vessels having the anion exchangeresin particles disposed thereon. Also, sheets or strips ofoil-resistant material, e.g., plastic, having anion exchange resinparticles adhering thereto can be suspended in the oil during storage.The resin in finely divided form, so as to minimize settling, can

a lso be metered into the oil as it is pumped into the' storagecontainer and recovered from the oil by filtration:

as 'the oil is removed from storage.

While the invention can be used in large storage ves-:

sels of the type emp'oyed in petroleum refineries, it is well-adaptedfor use in the smaller tanks of jobbers or be maintained When the resinsare no longer capable offmaina within the range of 4:1 to 1:4.

4 In order to demonstrate the effectiveness in mixed-dis tillate fuel"oils of stronglybasieanion exchange resins of the class disclosed above,various tests were carried out,vi;ncluding alight stability test and along term storage test. The light stability test was carried out byexposing a 4 oz. sample of oil to be tested to a light source withperiods of 7 hours, during'which the oil was stored in. the dark-Theltest was completed after 72 hours exposure'tovthelight. Visualestimates were made of the sludge and color after each complete, elevenhour, fonj off cycler The exposure to light was accomplished by puttingsamples of fuel oil in 4 oz. flint. glass bottles. These bottles wereplaced in an enclosure adjacent a light; I 7

source whichwas a Hanovia, 52353314 type burner;

Analytical Model quartz lamp. The light so urce was i made intermittentby passing light from thevahove lamp through a rotating, slitted drum."A Corning polished glass filter No. 9863 (24004000 angstroms) wasinter-r posed between the lightsource and the oil sample bot ties.Thespeed of the rotating drum was 1 revolution in 3,;seconds. The evenlyspaced, light-transmitting slits The distance Trace, Light,. Medium orHeavy. Seventy-two hours exposure under the conditions ofthis testcorrespond ap-.

proximately to 1 /2 to 2 years of normal storage in actual usage. Thelong term storage stability test was carried out by pouring 1500 ml; ofthe fuel to be tested into a two-quart Mason jar and immersing an 8 x1%" x & SAE 1020 cold rolled steel strip in the oil. The steel surfaceto oil ratio approximates that existing in a 5 5 gallon steel drum. Thejar was then closed with a vented lid and was stored in ,total darknessat ambient atmospheric temperature.

--- Periodic sampling and testing were carried out as rapidly aspossiblein subdued light. The extent of deterioration of, the fuel wasdetermined by the amount of precipitate observed and designated asTrace, Light, Medium or. Heal/1y. Any staining or corrosion of the steelstrip was note In the following table there are given the results oflight stability and storagetests made on mixed fuel oils of the.character indicated, both in the absence of a resin, and in contact witha strongly basic anion exchange resin of the class disclosed above. Theresin employed in these tests is adequately identified as the hydroxideform of a porous, quaternized chloromethylated copolymer ofaboutw97percent styrene and, about 3 percent divinyl benzene, that has beenquaternized with dimethyl ethanol amine. The chloride form of aresinessentially identical with the foregoing is marketed as AmberlitcIRA 411.". The chloromethylated copolymer, as such, contained inexcess'of 2 percent chlorine. The hydroxide form of the resin used inthe tests was prepared by placing the corresponding chloride form of theresin in a chromatographic tube to a depth such that the height todiameter 8 Total exchange capacity:

Meq./ml. wet resin- 0.7. Meq./g. dry resin 3.0.

Typical wet screen analysis ratio of the resin column was approximately10 to l. 5

The resin was then washed with 10 times its, volume of Standard screens)a solution of percent sodium. hydroxide, which was 'Sizeof mesh; Percentretained followed with distilled water washing until the eluate was19:1. no longer basic. The resin was. then dried under vacuum 7 for 3hours. The relatively dry resin then. was, suitably 10 29,3 hydrated bystirring'in'a. container with an excess of water for 15 minutes. Afterdecanting the excess water 70v w .7 l 0,5 the resin was filteredthrough. a Buchner funnel. (.under Finesicemem: Lessfljafl 2%.

suction) to remove surface water.- The. moist res1n',.pre- I paredessentially as indicated, was then placedin a per 15 No. 2 fuel oildistillate is defined in the ASTM Standimeable, muslin container and thelatter was substantially centrally suspended by a cord in the fuel oils.The by droxide form of the resin as prepared aboveis referredtohereinafter as Resin A. i

ards on Petroleum Products and Lubricants for 1956 under the designationD396-48T.

The following Table I light stability tests:

TABLE I Blend A Example I Example II Example III Sample Make-up:

Fuel Oil Blend, Vol. Percent- A. 31.3% West Texas, Doctor-Sweetened,Straight Run No. 2 Fuel Oil Distillate; 21.3% Virgin S'.R. No. 2 FuelOil Distillate;

47.4% Distillate. B. 31.3% West Texas, Doctor-Sweetened, No.

Fuel Oil Distillate; 21.3% Virgin S.R. No.

Oat. Cracked No. 2 Fuel Oil Fuel Oil Distillate? 47.4% Cat. Cracked No.2 Fuel Oil Distillate. Ion-Exchange Resin A in Contact with Fuel Oil-G./ Ml

1 Water Saturation of Resin A, Wt. Percent Inspections:

Color, ASTM Uni n Gravity, API

Specific Gravity, 60/60 F Neutralization Value Total Acid Number" TotalBase No Stability Test, Intermittent Ultra gh Glass Container, AfterExposure to Light, Appear- Trace of Stein on ance. Bottom. QualitativeEstimate of Sludge- I 36 Hours Med1um+... Tracel-... Med1um+ Trace-F...Trace-l 72 Hours Heavy-- Very Heavy- Light+ Heavy. Color, ASTM Union 4-4- 3.5- 3.5.

The corresponding chloride form of the commercial resin has thefollowing characteristics:

Physical form Uniform, bead-like porous particles. Density as supplied,lbs. per cu. ft..- 41.

Moisture content as supplied, per- It will be seen, from the foregoingtable that a strongly basic anionexchange resin of the class disclosedwill effect a substantial improvement in the stability of mixed catalytically cracked and straight run fuel oil distillates. It willalso beseen that the stability imparted by contact with the resin is reducedwhen using a resinv of relatively lower moisture content.

cent 53-63. In the following Table II. there are tabulated the results.

Screen grading (wet) mesh (U.S. obtained in the long term storage testscarried out on a standard screens) 20-50- 55 mixed distillate fuel oilalone and stored in contact with Efiective size, mm- 0.35-0.50. Resin A.

TABLE II Blend 0 Example III- Sample Make-Up:

Fuel Oil Blend, Vol. Percent- C. 33.3% Doctor-Sweetened W.T.S.R. No. 100100.

2 Fuel Oil Distillate; 33.3% Coastal S.R No. 2 Fuel Oil Distillate;33.3% Fluid Cat. Cracked No. 2 Fuel Oil Distillate.

Resin A- Grams per 1500 M1. Fuel Oil Weight Percent Moisture Content ofResin, Wt. Percent (Approx). Storage Stability Test:

After 6 months- After 1 year- Existent Insolubles (Visual)- Steel Strip,Appearance Existent Insolubles, Mg./l00 M1 Color, ASTM Union presentsthe data obtained in the r answer? From the data presented in theforegoing table it will be apparent that mixtures of catalyticallycracked and straight run fuel oil distillates are stabilized by.maintenance in contact during storage with a strongly basic anionexchange resin. It will be understood that the present invention isnotlimited to the specific embodiments given herein, and that otherdistillate fuel oil blends and other strongly basic anionexchange resinsof the class disclosed herein can be substituted for the correspondingsubstances in thespecificexamples in, the same or equivalentproportions. For example, for Resin Athere can be substituted thewater-saturated, hydroxide formof a porous, trimethyl amine-quaternizedchloromethylated copolymer of about 97 percent styrene and about 3percent divinyl benzene, or the saturated hydroxide form of a trimethylamine-quaternized chloromethylated copolymer of 97.5 percent styrene, 1percent divinyl benzene, and 1.5 percent ethyl styrene, and the like.Examples of commercial quaternary ammonium type resins that can. be usedinclude, in addition, to Amberlite IRA 411, Amberlite IRA 400, AmberliteIRA 401, "Amberlite IRA 410, Dowex 1 and Dowex 2.

As another example of the practice of our invention, 3000 grams of amoisture saturated, trimethyl aminequaternized chloromethylatedcopolymer of 96 percent styrene and 4 percent divinyl benzene, in thehydroxide form, prepared from the commercially obtained correspondingchloride form as described in connection with Resin A, is suspended inten equal portions in muslin bags at about equally spaced locations nearthe bottom of a cylindrical, 500 gallon storage tank to which there isadded 500 gallons of fresh, No. 2 fuel oil (50-50 by volume straight runand catalytically cracked distillate). After six months at ambientconditions, the tank is emptied. The resin is collected and afterremoval of its volume of 8 percent aqueous sodium hydroxide, waterwashed, and returned while Wet to the tank for further Ilse.

All of the resins disclosed are regeneratable by treat? ment with dilutecaustic, for example, by the same procedure described in connection withthe generation of resin A from its corresponding'chloride form.

The use of stronglybasic, anion exchange resins is essential to theinvention. Thus, for example, when a weakly basic, oil-insoluble, anionexchange material,

on the other hand, is one which on titration under the same conditionswill show a titration curve like that of a weak base, such as ammoniumhydroxide.

If desired, there may be added to fuel oils of the class disclosedherein, preferably, but not necessarily, after storage in contact withthe anion exchange resin, sludge inhibitors, oxidation inhibitors,corrosion inhibitors, ignition quality improvers, combustionimproversand/or other additives adapted to improve the oils in one or morerespects. 1

Many modifications and variations of the invention as described hereinwill suggest themselves to those skilled in the art. Obviously, thesecan be resorted to without departing from the spirit or scope of theinvention. Therefore, only such limitations should be imposed in thepresent invention as are indicated in the appended claims. l

We claim: 1 t I? 1. A process for stabilizing fuel oil comprisingmaintaining a mixture of catalytically cracked and straight run fuel oildistillates that normally tends to deposit sludge during storage incontact with a minor proportion, suflicient to stabilize the oils, of astrongly basic anion exchange resin that comprises a polymeric matrixgroups associated therewith substantially throughout the period ofstorage of said mixture of oils at ambient atmospheric temperature,where the moisture content of t the resin is at least about 25 weightpercent.

2. A process for stabilizing fuel oil comprising maintaining a mixtureof catalytically cracked and straight run fuel oil distillates thatnormally tends to deposit sludge during storage in contact with a minorproportion, sufiicient to stabilize the oils, of a strongly basic anionexchange resin substantially throughout the period adhering fuel on, theresin is regenerated with ten times jfpf storage of said mixture of oilsat ambient atmospheric temperature, said resin being the hydroxide formof a tertiary aminequ'aternized haloalkylated copolymer of about 80 to99.9 percent of a monovinyl aromatic hydrocarbon and about 0.1 to 20percent divinyl aromatic hydrocarbon, where the moisture content of theresin is at least about 25 weight percent.

calcium hydroxyapatite, in the proportion of about 2 grams per 1500 ml.of oil, was suspended in a run-of the-refinery, mixed distillate fueloil and subjected to the long term storage stability test, both theuninhibited and the inhibited oil showed heavy sludge deposits afterfour months. The explanation for this is believed to reside in the factthat weakly basic anion exchange materials.

are insufliciently basic to react completely with all of the weaklyacidic sludge and color precursors pr'es'ent'in mixed distillate fueloil. The resins of the class disclosed herein possess a basicitycomparable to that of sodium hydroxide.

It is to be emphasized that the resins disclosed herein.

3. The process of claim 2 where the copolymer contains about 0.5 to 6percent divinyl aromatic hydrocartaining a mixture of catalyticallycracked and straight run fuel oil distillates that normally tends todeposit sludge during storage in contact with a minor proportion of astrongly basic anion exchange resin substantially throughout the periodof storage of said mixture of oils at ambient atmospheric temperature,said resin being the hydroxide form of a tertiary amine-quaternizedhaloalkylated copolymer of about 94 to 99.5 percent of a bility of theoil. .Mere once-through contacting the oil with the resin, as bypercolation through a bed of the latter, is not suflicient. As a matterof fact, when this procedure was followed with fuel oil blend C andresin A, the treated oil was found to deposit more sludge than theuntreated oil.

Proportions mentioned herein are by weight where not specifiedotherwise.

Strongly basic anion exchange resins'may be defined as those which ontitration in a concentrated potassium chloride water solution, e.g., an0.5 normal solution, with an equivalent amount of hydrochloric acid,will show a titration eurve'like that of a strong base, such as sodiumhydroxide. A weakly basic anion exchange resin,

monovinyl aromatic hydrocarbon and about 0.5 to 6 percent of a divinylaromatic hydrocarbon, where the moisture content of the resin is atleast about 35 percent, where the tertiary amine substituents eachcontain 1 to 7 carbon atoms, and where the haloalkyl group contains 1 to4 carbon atoms.

6. The process of claim 5 where the tertiary amine is 'dirnethyl ethanolamine and the haloalkyl group is chloromethyl.

7. The process of claim 5 where the tertiary amine is trimethyl amineand the haloalkyl group is chloromethyl.

References Cited in the file of this patent UNITED STATES PATENTSCoonradt et al. Apr. 22. 1958

1. A PROCESS FOR STABILIZING FUEL OIL COMPRISING MAINTAINING A MIXTURE OF CATALYTICALLY CRACKED AND STRAIGHT RUN FUEL OIL DISTILLATES THAT NORMALLY TENDS TO DEPOSIT SLUDGE DURING STORAGE IN CONTACT WITH A MINOR PROPORTION, SUFFICIENT TO STABILIZE THE OILS, OF A STRONGLY BASIC ANION EXCHANGE RESIN THAT COMPRISES A POLYMERIC MATRIX HAVING A PLURALITY OF QUATERNARY AMMONIUM HYDROXIDE GROUPS ASSOCIATED THEREWITH SUBSTANTIALLY THROUGHOUT THE PERIOD OF STORAGE OF SAID MIXTURE OF OILS AT AMBIENT ATMOSPHERIC TEMPERATURE, WHERE THE MOISTURE CONTENT OF THE RESIN IS AT LEAST ABOUT 25 WEIGHT PERCENT. 